Our knowledge of frequency, severity, prognosis and risk factors for neuropathy in diabetics is incomplete or in error because surveys were not population-based, patients were not classified as insulin-dependent (ID) or non insulin-dependent (NID), surveillance of metabolic and risk factors was not obtained, inadequate or not prospective, and neuropathic assessment was too limited, uncontrolled and unquantitated to judge sensitivity and specificity and type and severity of neuropathy. This lack of reliable information on natural history of diabetic neuropathy adversely affects diabetic care and health and research planning. The serious shortcomings of previous studies are to be remedied in this continuation of a population-based cross-sectional and longitudinal study of neuropathy among all insulin-dependent (ID) and a sample of those with non-insulin dependent (NID) diabetic patients in Rochester, MN. Our intent is to: 1) estimate age- and sex-specific prevalence rates of diabetic neuropathy by type and severity; 2) elucidate the natural history; 3) characterize neuropathic symptoms and deficits; 4) assess risk factors; 5) estimate health care costs; 6) relate neuropathy to retinopathy and nephropathy; 7) assess minimal criteria for diagnosis of neuropathy; 8) develop and evaluate an approach to assess functional staging; 9) test the validity of various criteria in classification; and 10) characterize the neurologic symptoms and deficits using a battery of validated tests. Definition of motor, sensory, and autonomic symptoms are to be evaluated using validated measures of symptoms and deficits: neuropathy symptom score (NSS), neuropathy symptom profile (NSP), neurologic disability score (NDS), nerve conduction and electromyography, vibratory (VDT) and cooling (CDT) detection thresholds and autonomic tests. The sensitivity and specificity of these tests are validated against quantitated neuropathologic abnormality of sural nerve. Risk factors for diabetic complications, neuropathic symptoms and deficits, and type and degree of retinopathy complications, neuropathic symptoms and deficits, and type and degree of retinopathy and nephropathy are prospectively evaluated at intervals of time over four years so as to estimate progression and outcome and the role of risk factors. This is the first prospectively designed cross-sectional and longitudinal epidemiologic study of diabetic neuropathy employing metabolic surveillance, analysis of nerve metabolic derangement and validated tests of motor, sensory and autonomic dysfunction.